Machines for compression molding closure shells, or compression molding sealing liners within closure shells, typically include a turret or carousel that rotates around a vertical axis. A plurality of molds are provided around the periphery of the carousel, in the form of male and female mold sections that are aligned along vertical axes parallel to the axis of rotation. Cams drive one or both of the mold sections of each pair between an open position, in which a molded part is stripped from the male mold section and a charge of plastic material is placed in the female mold section, and a closed position in which the male and female mold sections are brought together to compression mold the shell or liner. In a liner machine, premade shells are placed in a nest when the mold sections are open, and a charge or pellet of liner material is placed within the shell before the molds are closed. U.S. patents that illustrate machines of this type for compression molding plastic closure shells include U.S. Pat. Nos. 5,670,100, 5,989,007, 6,074,583 and 6,478,568. U.S. patents that illustrate machines of this type for compression molding sealing liners within closure shells include U.S. Pat. No. 5,451,360.
Although vertical axis carousel-type machines of the noted type have enjoyed substantial commercial acceptance and success, innovation remains desirable. In particular, in vertical axis carousel-type machines, the mold forces and the weight of the rotating equipment are parallel to the vertical axis of rotation, creating a bending moment with respect to the axis of rotation and the bearings and shaft that support the carousel. Carousel-type machines also require a substantial amount of valuable floor space in a manufacturing facility. It is a general object of the present disclosure, in accordance with one aspect of the disclosure, to provide a method and apparatus for compression molding plastic articles, such as plastic closures and plastic liners within closure shells, which reduce the forces applied to the support frame and bearings, reduce maintenance requirements and the amount of energy needed to operate the machine, and/or reduce the amount of floor space required per machine.
The present disclosure involves a number of aspects that can be implemented separately from or in combination with each other.
A compression molding machine in accordance with a first aspect of the present disclosure includes a wheel mounted for rotation around a horizontal axis and a plurality of angularly spaced molds disposed around the wheel. Each of the molds includes a first mold segment and a second mold segment disposed radially outwardly of the first mold segment. Each of the second mold segments is movable by a cam radially with respect to the associated first mold segment between a radially inner closed position with the first mold segment for compression molding a plastic article, and a radially outer open position spaced from the associated first mold segment for removing a molded article from the mold and placing a mold charge into the mold.
In preferred embodiments of the disclosure, the cam includes a first cam portion for engaging the second mold segments in sequence and moving the second mold segments from the closed position to the open position, and a second cam portion positioned downstream of the first cam portion (with respect to the direction of wheel rotation) for moving the second mold segments in sequence from the open position to the closed position. In some presently preferred embodiments, a cam displacement wheel is disposed adjacent to the second cam portion, such as by being rotatably mounted on the second cam portion, for moving the second mold segments toward the closed position. The cam displacement wheel rapidly moves the second mold segments from the open position toward the closed position.
In another aspect of the disclosure, the second cam portion may be movably mounted with respect to the first cam portion, preferably by being pivotally mounted at the downstream end of the first cam portion. The second cam portion in this aspect of the disclosure preferably is coupled to a spring-biased latch for release in the event of excess force applied to the second cam portion by the cam followers on the second mold segments.
A machine for compression molding plastic articles, in accordance with a further aspect of the disclosure, includes an array of compression molds mounted on a support (such as a vertical or horizontal mold wheel) for movement through a defined mold path. A cam is disposed adjacent to the support to engage the molds in sequence and move at least one segment of each mold between open and closed positions. The cam has a first portion for opening the molds, a second portion for closing the molds in sequence, and a pivot mounting the second cam portion to the first cam portion. A latch holds the second cam portion in a first position for closing the molds in sequence, and is responsive to excess force on the second cam portion to release said second cam portion to pivot to a second position spaced from the path.
A machine for molding plastic articles, in accordance with yet another aspect of the disclosure, includes at least one mold carried by a movable support, such as a vertical or horizontal mold wheel. The mold includes at least one mold segment that is movable between open and closed positions. At least one cam is disposed adjacent to the support for engaging the at least one mold segment. The at least one cam includes a first cam portion for moving the mold segment to an open position, a second cam portion for moving the mold segment to a closed position, and a cam displacement wheel disposed adjacent to the first and second cam portions for displacing the mold segment from the first cam portion onto the second cam portion. The cam displacement wheel preferably is mounted for rotation in synchronism with motion of the support, most preferably at constant velocity. The at least one mold segment preferably has a cam follower for engaging the first and second cam portions in sequence, and the cam displacement wheel has at least one arm for engaging the cam follower on the first cam portion and displacing the cam follower onto the second cam portion.
A machine for handling articles (e.g., molding plastic articles), in accordance with a further aspect of the disclosure, includes at least one tool (e.g., a mold) carried by a movable support, such as a vertical or horizontal mold wheel. The tool includes at least one tool segment that is movable between first and second (e.g., open and closed) positions. At least one cam is disposed adjacent to the support for engaging the at least one tool segment. The at least one cam includes a first cam portion for moving the tool segment to an open position, a second cam portion for moving the tool segment to a closed position, and a cam displacement wheel disposed adjacent to the first and second cam portions for displacing the tool segment from the first cam portion onto the second cam portion. The cam displacement wheel preferably is mounted for rotation in synchronism with motion of the support, most preferably at constant velocity. The at least one tool segment preferably has a cam follower for engaging the first and second cam portions in sequence, and the cam displacement wheel has at least one arm for engaging the cam follower on the first cam portion and displacing the cam follower onto the second cam portion.